At present, it is difficult to imagine a car not equipped with power steering. The amplifier can be electric (), hydraulic (power steering) or electro-hydraulic (). However, power steering remains the most common type at the moment. It is designed in such a way that even if it fails, the ability to drive a car will remain. In this article, we will analyze its main functions and learn in detail what it consists of.

Functions and purpose of power steering

Steering rack with hydraulic booster

Hydraulic power steering (PSS) is a steering element in which additional force when turning the steering wheel is generated by hydraulic pressure.

For cars The main purpose of power steering is to provide comfort. Driving a vehicle equipped with hydraulic power steering is easy and convenient. In addition, the driver does not need to make a full five or six turns of the steering wheel in the direction of the turn to complete the maneuver. This state of affairs is especially true when parking and maneuvering in narrow areas.

Maintaining controllability of the car and softening the shocks transmitted to the steering wheel as a result of the collision of the steered wheels on bumps in the road is also an important function of the hydraulic booster.

hydraulic power requirements

For the effective operation of the power steering, the following requirements are imposed on it:

• system reliability and quiet operation;
• ease of maintenance and minimum size devices;
• manufacturability and environmental safety;
• small turning moment on the wheel with automatic return to neutral position;
• lightness and smoothness of steering;
• ensuring kinematic follow-up action - correspondence between the angles of rotation of the steered wheels and the steering wheel;
• ensuring power following action - proportionality between the forces of resistance to the rotation of the steered wheels and the force on the steering wheel;
• the ability to drive a car in the event of a system failure.

Power steering device

The main components of the power steering

The power steering is installed on any type. For passenger cars, the most common rack and pinion mechanism. In this case, the power steering scheme is as follows:

• reservoir for working fluid;
• oil pump;
• spool valve;
• hydraulic cylinder;
• connecting hoses.

power steering reservoir

power steering reservoir

A filter element and a dipstick are installed in the tank or reservoir for the working fluid to control the oil level. With the help of oil, the rubbing pairs of mechanisms are lubricated and the force is transmitted from the pump to the hydraulic cylinder. A grid serves as a filter from dirt and metal chips that occur during operation in the tank.

The liquid level inside the tank can be checked visually when the tank is made of translucent plastic. If the plastic is opaque or a metal tank is used, the liquid level is checked with a dipstick.

In some vehicles, the fluid level can only be checked after running the engine for a short time, or by turning the steering wheel several times in different directions while the vehicle is idling.

Special notches are made on the probes or reservoirs, both for a “cold” engine, and for a “hot” one that has already been working for some time. Also, the required liquid level can be determined using the “Max” and “Min” marks.

power steering pump

Power Steering Vane Pump

It is necessary in order to maintain the desired pressure in the system, as well as to circulate the oil. The pump is mounted on the engine block and is driven by a pulley crankshaft with a drive belt.

Structurally, the pump can be different types. The most common are vane pumps, which are characterized by high efficiency and wear resistance. The device is made in a metal case with a rotor with blades rotating inside it.

In the process of rotation, the blades capture the working fluid and supply it under pressure to the distributor and then to the hydraulic cylinder.

The pump is driven by a crankshaft pulley, so its performance and pressure depend on the number of engine revolutions. To maintain the required pressure in the power steering, special valve. The pressure that the pump creates in the system can reach up to 100-150 bar.

Depending on the type of control, oil pumps are divided into adjustable and unregulated:

• adjustable pumps maintain a constant pressure by changing the productive part of the pump;
• constant pressure in non-regulated pumps is maintained by a pressure reducing valve.

The pressure reducing valve is a pneumatic or hydraulic throttle that operates automatically and controls the level of oil pressure.

Power steering distributor

Schematic device of the distributor

The hydraulic booster distributor is mounted on the steering shaft or on the elements. Its purpose is to direct the flow of the working fluid into the corresponding cavity of the hydraulic cylinder or back into the reservoir.

The main elements of the distributor are the torsion bar, the rotary spool and the distributor shaft. A torsion bar is a thin springy metal rod that twists under the action of a torque. The spool and distributor shaft are two cylindrical parts with fluid channels inserted into each other. The spool is connected to the steering gear, and the distributor shaft is connected to cardan shaft, that is, with a steering wheel. The torsion bar is fixed at one end to the distributor shaft, its other end is installed in the rotary spool.

The distributor can be axial, in which the spool moves forward, and rotary - here the spool rotates.

Hydraulic cylinder and connecting hoses

The hydraulic cylinder is built into the rack and consists of a piston and a rod that moves the rack under the action of fluid pressure.

The scheme of fluid circulation in the hydraulic booster

High pressure connecting hoses provide oil circulation between the distributor, hydraulic cylinder and pump. Oil from the tank to the pump and from the distributor back to the tank flows through low pressure hoses.

The principle of operation of the power steering

Consider several modes of operation of the hydraulic booster when turning the wheels in any direction:

1. The car is stationary, the wheels are straight ahead. At the moment, the hydraulic booster is not working and the liquid is simply pumped through the system by the pump (from the tank to the distributor and back).
2. The driver starts to turn steering wheel. The torque from the steering wheel is transmitted to the distributor shaft and then to the torsion bar, which begins to twist. The rotary valve does not rotate at this moment, since it is prevented from doing so by the friction force that prevents the wheels from turning. Moving relative to the spool, the distributor shaft opens a channel for fluid to enter one of the cavities of the hydraulic cylinder (depending on where the steering wheel is turned). Thus, all fluid under pressure is directed to the hydraulic cylinder. The liquid from the second cavity of the hydraulic cylinder enters the drain line and then into the tank. The liquid presses on the piston with the rod, due to which the wheels move and turn.
3. The driver has stopped turning the steering wheel, but continues to hold it in the turned position. The steering rack, moving, rotates the rotary spool and aligns it with the distributor shaft. At this point, the distributor is set to neutral and the fluid again simply circulates through the system without doing any work, just as with the straight wheels.
4. The driver “turned” the steering wheel to the extreme position and continues to hold it. This mode is the most difficult for the hydraulic booster, since the distributor cannot return to the neutral position, and all fluid circulation occurs inside the pump, which is accompanied by increased noise from its operation. But it is worth releasing the steering wheel, and the system will return to normal.

The scheme of the hydraulic booster

The power steering is designed in such a way that if it fails steering will continue to work and the ability to drive a car will remain.

The frequency of fluid replacement in power steering

In theory working fluid can be used throughout the life of the car, but it is recommended to change the oil periodically.

Replacement times depend on the intensity of use. vehicle. At average annual mileage 10-20 thousand km, it is enough to change the oil every two to three years. If the machine is used more often, then the fluid should be changed more often.

As a result of the operation of the hydraulic booster, the temperature of its elements rises. Due to this, the oil is also heated, which leads to a deterioration in its physical properties. If foreign particles or the smell of burnt oil are noticed when monitoring the condition of the fluid, then it is time for a replacement.

steering rack - This is a vehicle assembly that is designed to control the wheels. The driver turns the steering wheel, through special shafts the "turn" is transmitted to the rail, which transmits the force to the wheels. Thus, they deviate to the desired angle. Thanks to this design, the machine can go around obstacles, turn, maneuver, and not move in a straight line.

This node evolves along with the machine, before it was a rather primitive design, now more and more technologies are being put into control. But to this day, there are only three main types of steering racks. Let's take a closer look.

Types of steering racks

• Normal, without amplifiers . It was used back in the 70s - 80s of the last century on 90% of cars. Here, all the effort of turning the steering wheel lies on the driver, there are no amplifiers, and therefore it is not always easy to turn the steering wheel.
• Steering rack with power steering or power steering. In fact, this is the same ordinary rail, only a special pump and a closed circuit with seals are added to it (where special liquid), which helps turn the steering wheel. That is, the driver does not need to make a lot of effort to turn the steering wheel. This is especially valuable on heavy vehicles (trucks, buses and SUVs).
• Steering rack with EUROM or electric power steering. This is a dry type of amplifier, no oil is used here, and the principle of operation is completely different. Next to the shaft is an electric motor with a gear (powered from the on-board network), which helps to turn the steering wheel. He is ordered by the ECU, he sees where the wheels deviate and orders the electric motor to help in the turn.

To exaggerate, the types are divided as follows: - conventional mechanics with 100% use of muscle power, a rail with hydraulic booster and electric booster.

How is the steering rack arranged?

The steering rack of a car is a device, the purpose of which is to convert the driver's effort during the impact on the steering wheel in the passenger compartment, which is necessary to ensure the rotation of the wheels of the car.

Today there are three types of steering racks, the principle of operation of which is different.
hydraulic steering rack. It is used in almost all passenger cars that are produced today. Provides a fairly comfortable driving experience, since hydraulic power steering is used, so that the driver needs to make a minimum of effort. Mechanical steering rack. The device of this element is very simple. At one end of the rack is a gear mechanism that contacts the rack. The latter interacts with the steering wheel drive.

Electric steering rack. Its difference from the hydraulic counterpart is that hydraulics is not used. To increase the efforts of the driver, the car is equipped with a separate electric motor. The device of the steering rack, as well as the principle of its operation, depend on the characteristic features of each car. The steering rack can have an upper or lower location, which also depends on the model of the vehicle. The overhead steering racks are mounted behind the engine, they are attached to car body. Steering racks with a lower location are attached from below, they are connected to the body, subframe or beam.

Troubleshooting the steering rack

Steering rack malfunctions are quite common, since this assembly and the entire steering system on domestic roads are subjected to increased loads. A broken rail can be detected independently, guided by a number of signs:

If these symptoms of rack failure appear, it is recommended not to delay the dismantling of the steering gear for inspection and troubleshooting in order to minimize repair costs.

1. it became harder to rotate the steering wheel, or it periodically bites (difficult rotation is observed only periodically in certain positions of the steering wheel);
2. there is a knock of the front suspension, which clearly “gives to the steering wheel”;
3. the power steering pump is noisy;
4. steering wheel play, which means rack play;
5. leakage of oil from the steering rack, which is often accompanied by a noticeable increase in steering force and resulting in this action noises.

The appearance of such signs indicates that steering rack device somewhere broken and this mechanism diagnostics and further repair is required.

Repair features

Even before the start of disassembly of the steering mechanism, it is required to conduct a thorough inspection of the rack and all associated components (ball, tie rods, hub bearings, etc.). This will help to localize the problem from the very beginning. Further, the steering mechanism is completely or partially dismantled and the breakdown is eliminated. The rail is a repairable unit, therefore, if it fails complete replacement is not always a mandatory decision.

Without partial disassembly of the entire mechanism, it is almost never possible to troubleshoot problems associated with steering racks due to the specifics of the location and connection of this node.

A do-it-yourself corrected steering rack is also quite likely, with the exception of repairing electronic racks that need special tuning. However, in order to achieve optimal quality it is always better to trust this work to specialists and give preference to replacing rails instead of repairing them, given the importance and high wear rate of this assembly.

• It is necessary to monitor the condition of the protective anthers.
• Do not hold the steering wheel in the extreme position for more than 5 seconds. Do not spin the engine in the extreme position of the steering wheel. This leads to wear of the power steering pump, an increase in the load on the parts of the steering rack, steering gear; contamination of the hydraulic booster system, breakdown of the hydraulic booster seals.
• In winter, do not turn the steering wheel to leave a parking space immediately after the engine has warmed up. Turn the steering wheel in short, smooth motions. This is necessary to warm up the oil in the power steering system.
• Personally supervise all operations at the service station, one way or another affecting the elements of the steering. Often, when adjusting the alignment, the mechanics loosen the anther clamp, and forget to tighten it back. Moreover, they do the work with dirty hands! Sand and dirt can ruin the rack and power steering in just two days, and even faster.

The steering rack or, more correctly, the rack and pinion steering mechanism is a design that converts the rotation of the steering shaft into horizontal movement of the rods. The link between the driver who turns the steering wheel and the wheels. Most modern cars have this type of steering gear, which has replaced the worm gear.

However, this is not a logical continuation of the worm gear. For the first time, the steering rack was installed on cars of the nineteenth century, in a primitive variation of a gear on the steering shaft and a rack meshed with it with teeth.

Later, it was replaced by complex mechanisms, including a worm, only at the end of the twentieth century, designers returned to the rack-and-pinion design. The design became so successful that modernization continues to this day.

Steering rack device

The connection of the rack with the wheels occurs due to the steering rods, which, with the help of tips, set the angles of rotation of the wheels.

There are three types of rack mechanisms:

1. Mechanical.
2. Hydraulic.
3. Electric.

The steering rack layout will vary depending on the type of mechanism, but general principle will remain the same.

Mechanical steering rack

It is the simplest type of rail, but at the same time the most versatile, because. the mechanism is installed on both front-wheel drive and rear-wheel drive cars. Turning the wheels is carried out only with the help of physical force. A feature of this design is the variable gear ratio. This means that the pitch of the teeth changes from the middle to the edges. When driving at high speeds, when the steering angles are minimal, the effect of a heavy steering wheel is created due to the large gear ratio. And in the parking mode, when the steering wheel is turned to the extreme positions, on the contrary, the gear ratio becomes low and the steering wheel is easy to turn.

The steering rack diagram includes:

• an aluminum crankcase with a cavity with special protection in the form of a rubber corrugation;
• drive gear or ordinary gear attached inside the housing with a special bearing;
• a spring that tightly presses the rack against the gear, thus ensuring a tight grip of the teeth;
• thrust joint bushing, works in a given interval and provides the required travel of the steering rack.

Electric steering rack

The principle lies in the operation of the electric motor, which transmits the force from the steering wheel as accurately as possible. The electric booster can be integrated into the rail or located on the steering shaft. This method allows installation significantly reduces the cost of construction, at the same time reduces safety.

The fact is that when the electric motor fails, the control becomes very tough, in fact, uncontrollable. The steering wheel simply does not give in, despite the efforts made. However, the device of the steering rack with an electric motor has a number of advantages that outweigh the disadvantages:

• high efficiency;
• simplicity and compactness;
• immunity to weather conditions;
• lack of working fluids;
• high reliability due to the absence of gaskets, seals, tubes;
• efficiency (the electric motor only works when the steering wheel is turned, and when high speed turns off);
• low cost;
• quick return of the steering wheel to the neutral position.

Hydraulic steering rack

The principle is to transfer force with the help of hydraulic fluid. This ensures accuracy and ease of driving. Thanks to hydraulic system the transfer of road irregularities to the steering wheel decreases and, having driven into a pit at speed, you will not tear out the steering wheel, since the blow will extinguish the hydraulic booster. But the high fluid pressure at the moment of impact will affect the state of the entire system.

The cons include:

• poor information content of the steering wheel, lack of good feedback;
• poor reliability due to high pressure at work;
• leakage and regular replacement of seals, gaskets, tubes;
• constant operation of the system, even if you stand still with the engine running, the pump will circulate fluid in the system;
• repair problems, have to change the fluid.

Despite a decent number of disadvantages, heavy vehicles have hydraulic steering, since the electric motor is not able to transmit such an effort that the fluid provides.

Electro-hydraulic steering rack

The logical continuation of the hydraulic rack was electro-hydraulic. This is a hybrid system with technology based on hydraulics, similar to power steering, but the pump is driven not by an engine, but by an electric motor. In this version, the lack of non-informative feedback was eliminated. The higher the speed, the less pressure the electric motor creates, giving a feeling of stiffness in the steering wheel.

Advantages and disadvantages of the rack and pinion mechanism

• simple small-sized design;
• reliability;
• light weight;
• precise transfer of force.

• good transmission of impacts of road surface irregularities;
• frequency of maintenance (tightening, oil change).

Outcome

The steering rack is one of the most important mechanisms of the car, which connects the steering wheel and wheels, and is also a connecting link for them. Fast, precise response and transmission of forces to the wheels is the key to your safety. Therefore, designers improve the steering rack device every year.

The power unit, with the help of which the front wheels of the car synchronously turn in the direction in which the driver turns the steering wheel. It is useful for every car owner to know the device of the steering rack, as well as the principle of its operation, since the safety of passengers and pedestrians depends on this device.

Principle of operation

Rack-and-pinion mechanism

Consider the principle of operation of the steering rack. When the driver turns the steering wheel, the force from it is transmitted further to the gear, which causes the rack to move. It moves to the left or right, and with it the steering rods move, which turn the hubs or steering knuckles. Accordingly, the wheels themselves are fixed on the hubs. As a result, when the driver turns the steering wheel, the front wheels of the car turn synchronously.

The rack and pinion steering mechanism is often equipped with a power steering, which significantly reduces the effort when the driver turns the steering wheel.

Device and main components

Steering rack diagram

Consider how the steering rack works. will be described in general. So, its main components:

• steering wheel (or steering wheel) - a device for controlling the movement of a car in a given direction;
• steering shaft - a metal rod that has splines (grooves) for fixing the steering wheel on one side, and on the other - splines for attaching the steering shaft itself to;
• steering rack - power unit, which consists of a rack and pinion. It is she who sets the rail in motion. This unit is assembled in a light alloy housing and fixed to the car body;
• steering rods - metal rods. Each rod has a thread on one side, and a hinged ball device on the opposite side, which also has a thread;
• steering tip - a part for screwing in thrust. Has a ball joint and internal thread.

Note that sometimes the steering mechanism has another component - the steering rack damper. This element is installed between the rods and the steering rack housing. The damper is a double acting shock absorber. The main task of the damper is to reduce vibrations on the steering wheel. The steering rack damper is often pre-installed on various SUVs, since this type of car most often travels on bad roads.

Types of steering racks

There are three main types of steering racks:

• Mechanical steering rack. It is the simplest version of the steering mechanism. Here, the rotation of the front wheels is carried out only due to the physical efforts of the driver. Often, to facilitate his work, a steering rack is installed that has a variable gear ratio. In it, the pitch of the teeth changes from the center to the edges. For the first time in history domestic auto such a rail was used on a VAZ-2110 car.
• Hydraulic steering rack. The main difference from the mechanical one is the presence (abbreviated power steering), which greatly facilitates the rotation of the steering wheel. In this case, the driver not only gets less tired behind the wheel, but also gets more safety while driving. The rail is widely used on modern cars.
• Electric steering rack. Here, the steering wheel is reinforced by an electric motor. Separately, it is worth noting the placement of the electric motor: it can be built into the steering column, located on the steering shaft or combined with a rack. The rack from the steering wheel has the highest efficiency, is economical and more reliable. You can read more about electric power steering at.

Advantages and disadvantages

First, about the advantages of rack and pinion steering:

• simplicity and small dimensions of the structure;
• light weight;
• no frequent maintenance required;
• good control accuracy;
• small price.

Now for the cons:

• transfers shocks from bumps in the roadway to the steering wheel;
• frequent malfunctions in the form of backlash and knocks in the rail;
• this mechanical device is limited to use in most cases on light vehicles with independent suspension steered wheels.

Despite its reliability, the service life of this power unit depends on the quality of the assembly of the car, the conditions of use, driving style, and storage conditions. If the machine is in dampness for a long time, the mechanism may simply rust. extreme riding over bumps and pits and other irregularities also reduces the life of the mechanical steering rack.

On passenger cars, rack and pinion steering remains the most common. This is facilitated, first of all, by the simplicity of the design, low cost mechanism, as well as its small dimensions.

Hello dear car enthusiasts! The principle of rack and pinion power transmission is not the first time used in the automotive industry in the form of a steering rack. Cremalier (French crémaillère) - one of many types mechanical transmission, which converts translational motion into rotational.

Remember the old, folding cameras that used rack and pinion to focus. But, we are talking about the steering rack of the car.

The steering rack of a car has long been an integral part of the steering. And. on almost all modern cars, a steering rack is used. This does not exclude the use of such types of steering mechanism as: worm gear or screw-ball nut.

Car steering rack device

So, we have already understood that the steering rack of a car is a mechanical device that converts the driver's effort when acting on the steering wheel, which is required to control the car (turning the wheels).

According to the principle of operation, steering racks are divided into three main types:

• Mechanical steering rack - has the simplest device. The gear mechanism located at the end of the steering column interacts with the gear rack, which, in turn, is connected to the steering gear (trapeze from).
• Hydraulic steering rack - installed on most modern cars. Carries out the most convenient and easy driving by connecting the power steering (power steering), which increases the effort applied by the driver.
• An electric steering rack differs from a hydraulic steering rack in that it does not have hydraulics, and the driver's efforts when steering the steering wheel are increased by an electric motor.

The principle of the device of steering racks differs only design features car brands.

The location of the steering rack may also be different depending on the brand of car:

• Top location - the steering rack is attached to the body and is located behind the engine.
• Bottom location - the steering rack is attached to the subframe, body or beam, from below.

Steering rack design (on the example of a gear rack)

• Carter. It is usually made from aluminum alloy. It has a cavity inside, which is protected by a corrugated cover.
• Drive gear mounted in the crankcase on bearings.
• The rack is pressed against the gear by a spring in order to ensure backlash-free engagement of the gear and rack teeth.
• The restrictive ring on one side and the tie rod bushing on the other limit the travel of the rack in the required range.

This scheme of the steering rack has a small gear ratio and allows you to quickly control the wheel in the right direction.

By the way, the designers of the BMW concern improved the steering rack by connecting it to the planetary mechanism. This scheme of the steering rack allows you to change the gear ratio of the gear depending on the speed of the car.

The principle of operation of the steering rack with hydraulic booster

So, let's find out in more detail why the steering wheel with power steering is spinning so easily. An integrated amplifier is when it is connected to the steering rack actuating mechanism power steering.

The power steering pump is driven by the engine using gears: belt or gear. It supplies high pressure hydraulic fluid to the spool valve. The spool valve is built into the crankcase (body) of the steering rack.

The main task of the spool valve is to control the force on the steering wheel and the dosage of hydraulic fluid to turn the steering rack. The dosing device, as a rule, is a torsion bar, which is built into the section of the rack steering shaft.

During parking or driving in the forward direction, there is no force on the steering rack. This means that the metering channels of the spool valve are blocked, and the oil is in the reservoir.

When you turn the steering wheel, the resistance of the wheels begins. At the same time, the torsion bar begins to twist: the greater the force on the steering wheel, the stronger. At this time, the spool valve opens the channels and supplies hydraulic fluid to the actuator - the steering rack. Here the oil is distributed in the right direction and pushes the rail.

Taking into account the fact that the steering rack is in constant intensive use, it is advisable for you, as a driver, to systematically monitor the health of its elements: anthers, seals, tubes.

It is not necessary to constantly climb under the car for this. Do not be lazy to visually check for oil leaks under the car.